I don't think it would be bug MC-62166, because the light surrounding the portal isn't a block. That glitch was fixed when I made this world.
I found out which block was providing the light, and that if I place a block next to it the block updates and stops producing the light.
We are now experimenting with it to find out how we did it.
@Blah you misunderstood the issue for being missing cobblestone, when infact the cobblestone was there.
Bug MC-62958 was very similar, but the chunk loading was more duplicating existing chunks (Appearance, not model and interaction, they were still the original chunk).
Bug MC-62958 looks more like invisible blocks and chunks.
The texture/model bug look similar but this was more drastic I think.
MC-62166 does sound a lot like this bug we are still getting, which is weird since it says it has been fixed.
Also, your bug MC-10890 does look a lot like someone just messed with your textures. Wrong animal textures wouldn't fit that perfectly to a wrong model.
We tried restarting the world and then his minecraft, but it still occurred.
How high was your FOV?
It's not a bug, it's a server plugin. Some servers mess around with stuff like that, and I'm not sure if it's fixable.
The cobblestone still generates, but it generates in the cave.
It's not a glitch or bug. On their snapshots they don't document them as fixing bugs, they document them as updating map colors.
Example of my maps next to someone else' maps.
Looks like the resolution is so high that the pixels become very thin and sometimes not visible at some angles.